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J. Romero del HombreBueno, E.-J. Lee, J. De Juan, N. M. Grzywacz, S. A. McFadden; Reduction in Nitric Oxide Synthase Immunoreactivity in Myopic Guinea-Pig Retinas. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3674.
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A progressive and excessive elongation of the ocular globe causes myopia, and evidence supports a retinal locus of control. In chicks, a nitric oxide synthase (NOS) inhibitor blocks form deprivation (FD) myopia and there is a reduction in iNOS mRNA expression in FD eyes. Changes in NOS activity have been reported to vary in FD guinea pig eyes. We investigated NOS immunoreactivity in retinas from myopic guinea pig eyes.
Myopia was induced in young guinea pig eyes using either FD diffusers or -4D lenses worn on one eye from 6 days of age for 12 days under a 12hr/12hr light/dark cycle. The untreated eye was used as a control. At P18, refractive error was measured in cyclopleged eyes and ocular length measured with ultrasound. Retinas were then extracted and the expression pattern and distribution of NOS immunoreactive neurons was studied by immunocytochemistry.
FD and -4D lens wear induced relative myopia (-3.9D; -3.7D) and ocular elongation (+108µm; +80µm) respectively after 12 days. In control and myopic retinas, NOS immunoreactivity was present in cone bipolar cells, Type I and Type II amacrine cells and displaced amacrine cells. In myopic retinas, the number of NOS immunoreactive cells in the ganglion cell layer was reduced by 45%, and this was not due to cell death, as we observed no TUNEL positive cells or activation of microglia. NOS-immunoreactive Type I amacrine cells also had less spines on their processes in myopic retinas.
The reduction in NOS immunoreactive displaced amacrine cells in the myopic mammalian eye, suggests that NOS is significantly down-regulated in rapidly growing eyes and implicates these cell types in the control of myopia.
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